Hi - the last couple of weeks I've begun building a bunch of modules running off +/-12v supply - there's so much great info about that it sometimes becomes a bit confusing..!..

What I'm wondering about is the interfacing of different modules - for example if an lfo outputs a signal of +/-5v around gnd, how is it best to apply it to a CV input that requires 0-10v input? I was thinking that a CV mixer may help - adding a variable DC voltage between say + or - 5 volts to shift the whole CV signal.. Does this sound as though I'm going in the wrong direction?

That sounds fine to me.
But I'd connect it just as it is and check it out first. Chances are you'll be able to get what you want without the hassle of the mixer. For example, even when you shift it up or down with the coarse tuning, on a 1V/Oct VCO +/-5 will still let the LFO sweep it up and down by 10 octaves!! I think it would be pretty rare that that wouldn't be enough._________________What makes a space ours, is what we put there, and what we do there.

What you are describing is one of the most common constructs in computer and electronic music - scale and offset. In computer music, you would:

S1 = (S * Scale) + Offset

Such a thing is pretty easy to in analog synths too, but I'm surprised how difficult it is in many modulars one finds out there. Moog modulars had a few CV input controls that allowed one to mix in various amounts of a a signal (either postive or negative). This was very useful._________________--Howard
my music and other stuff

Haven't yet made a CV mix with offset, but maybe if I have space & time I will do - - 'cos at the end of the day you sometimes need extra control and it'd be such a simple circuit.

Well, one thing that helped me figure out more of this (well, as well as reading thoroughly through most of the MFOS web pages) was building a circuit to provide X & Y cvs from a joystick.. I wondered for a long time how to set it up - 0v - 5v or ??? Well, with a bit of playing, it turned out best at +/- 12v -- 'cos the joystick is sprung, it starts by default at 0v (or so - hmm, a quantiser would be useful too!) and then it has a range of about + or - 5 volts --- which, I think, is pretty damn perfect!

Also currently have a couple of Aaron Cram's Attenuverter circuits - - its a great little utlity - attenuation and invertion - at centre its off, clockwise gives you positive to +1, and anti-clockwise gives you invertion to -1 --- simple and great : http://www.ori.org/~aaronc/synth/Attenuverter_V1.pdf

Also currently have a couple of Aaron Cram's Attenuverter circuits - - its a great little utlity - attenuation and invertion - at centre its off, clockwise gives you positive to +1, and anti-clockwise gives you invertion to -1 --- simple and great : http://www.ori.org/~aaronc/synth/Attenuverter_V1.pdf

Excellent. You can add an offset to that and you have a really useful circut (not that it's not already useful). That functionality is exactly what was on the early Moogs, BTW._________________--Howard
my music and other stuff

also, it's worth noting that the g2 demo (that runs standalone on a pc) has all of the possible options for how these things interface. you might experement with this as a "mockup" so you can see what kinds of modules you will need to accomplish your goals. i use the demo all the time to work out ideas.

Ahhh - yeah, I've actually got a micro modular, but its leant to someone at the moment 'cos the editor doesn't run on XP. Those nord digi-modulars really are fantastic - and that's a damn fine point about trying things out on them 'cos they're so quick and simple to use. YES.!.

It can run on XP though, although some have to set compatibility mode to win98 and others have to get different MIDI drivers._________________Jan
(yawning shifts perceived pitch, making things more interesting)

It can run on XP though, although some have to set compatibility mode to win98 and others have to get different MIDI drivers.

Really? For the micromodular, rather than the g2..?.. Wow, that'd be good - but what's the compatability mode? I've tried setting it up with a variety of different midi interfaces (& drivers) before and the computer never sees the micro.. I'd be mighty happy to get back to using it!_________________http://www.bugbrand.co.ukhttp://www.bugbrand.blogspot.com

Excellent. You can add an offset to that and you have a really useful circut (not that it's not already useful). That functionality is exactly what was on the early Moogs, BTW.

YES! Probably I will combine a couple Attenuverts with offsets and then straight into a CV mixer. USEFUL! Certainly at this stage where I'm still discovering how things control each other.

So why did such utilities not appear much in modulars? Is it to do with people tweaking controls so that you don't need extra utilities? (ie a well designed synth may only offer a relatively small number of controls 'cos the designer has been really selective?)

If you are going to build a CV mixer, then just make every input have one of those Attenuverters (great name). That would be a great mixer. Interesting about the offset control. If you put in on the summing node of the Attenuverter, then the offset will apply directly to the input signal. This is probably useful in some situations, but most of the time my guess is you'd end up wanting the offset to be added in after the Attenuverter. If that was the case, then if you have a CV mixer with say 4 Attenuverter inputs, you'd only need one offset for the entire mixer.

You can easilly patch up something like that with a Nord Modular using a CrossFader and an inverter. Why there isn't a pre-built circuit is anyone's guess.

If you are going to build an analog module, then for sure build of model of it on the Nord Modular. It will save lots of debugging and heart ache. Just be careful, you may end up like me - I do all my analog design now on that way. I haven't built any circuits in several years._________________--Howard
my music and other stuff

Yeah I'm looking forward to getting back to working with the MicroModular, but also very much liking putting together my first modular things... So no worries at the moment about giving up making circuits! Also, the MicroModular doesn't do very much delay... Yesterday I completed a voltage controlled delay using the PT2399 - the modulation circuit is still a little bit bugged, but the sounds so far are INCREDIBLE! You can change the delay time by playing a CV keyboard which is pretty damn ace and the chip gets really noisy (in a good way) when you slow the delay right down. Haven't yet set it up with the joystick controller either... Oh, the possibilities.!._________________http://www.bugbrand.co.ukhttp://www.bugbrand.blogspot.com

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